Treatment of hydrocarbon oils



Feb. 23,; 1943. F. H. BOTTOMLEY v 2,312,020

TREATMENT OF HYDROCARBON OILS Fild Dec. 18, 1940 TREATING STEP GAS .S'EPAMTIOM TREAT/1V6 STEP FFACTIONATION HZSREMOVYIL 17 Patented F eb. 23, 1943 TREATMENT OF HYDROCARBON OILS Francis Harold Bottomley, Big Spring, Tex., as-

signor, by mesne assignments, to The Gray Processes Corporatioma corporation of Delaware Application December 18, 1940, Serial No. 370,601

3 Claims.

This invention relates to an improved process for the treatment of hydrocarbon distillates and particularly those boiling within the motor fuel range.

More specifically, the invention relates to improvement of motor fuel characteristics of gasoline, particularly in regard to antiknock properties and stability in storage by treating them with an earth or clay type of refining agent. The invention has the further object of removing certain sulfur compounds which are particularly harmful to antiknock properties of gasolines and of reducing the total sulfur content of the distillate. At the same time, improvements are obtained in the quantity of distillate which may be treated by a given quantity of clay compared to the amount obtainable by conventional methods.

The use of earths and clays such as fullers earth and similar naturally occurring materials for the vapor or liquid phase refining of gasoline is well known to the industry. Such treatment has been largely used for improving color, gum content, susceptibility to inhibitors, and similar objectives without substantially affecting the sulfur content, the treatment being carried out on cracked gasolines at temperatures up to approximately 500 F. or thereabouts, at pressures of atmospheric to relatively high pressures of the order of 1000 lbs. per square inch. Motor fuels, particularly straight run and natural gasolines, have also been treated by means of naturally occurring earths, such as fullers earth, bauxite and the like, at temperatures in excess of 500 F. whereby desulfurization is efiected to a greater or lesser degree but when treating cracked gasolines this effect is soon reduced to a negligible value although the earth continues to remove gum and color forming materials. The normal operation of such processes is in the range of about 600 to 850 F. Naturally occurring earths with or without activation by steam or acids have also been used as catalysts for hydrocarbon conversions at temperatures substantially in excess of 850 F., say in the order of 900 to 1200 F., whereby motor fuels are produced from higher boiling oils, or the octane rating of low antiknock fuels is increased by catalytic reforming methods.

The present invention is an improvement in ment in the method used previously for refining distillates and more particularly of treating cracked gasolines by means of earth type agents in a two stage operation, the first of which is carried out at relatively low temperatures primarily to remove gums and the second step is carried out at relatively high temperature to remove or convert sulfur compounds.

In one specific embodiment, the present invention comprises a process for refining hydrocarbon distillate, particularly cracked motor fuel, to improve the properties thereof in respect to color, sulfur content, gum content, antiknock value, susceptibility to octane number increases with tetraethyl lead, etc., which comprises treating hydroqcarbon distillate containing said motor fuel with an earth or clay type treating agent under conditions such that gum-forming components are substantially removed by polymer ization, thereafter separating the gases and hydrogen sulfide from the normally liquid hydrocarbons of approximately gasoline boiling range, subjecting said liquid hydrocarbons in vapor phase to a secondary treatment with an earth type catalyst at a temperature substantially in excess of that used in the primary step whereby substantial desulfurization and improvement in antiknock characteristics is obtained, separating the treated motor fuel and removing hydrogen sulfide therefrom.

The invention is further understood by reference to the accompanying flow diagram which represents the process diagrammatically and should not be interpreted as limiting it in strict accordance therewith.

The distillate to be treated, Which is suitably cracked gasoline or blends containing cracked gasoline, may be introduced through line I and line 2 to primary treating step 3. The distillate may be in the form of an endpoint gasoline or may have a somewhat higher endpoint than gasoline. The vapors may or may not contain normally gaseous constituents of the cracking reaction as well as motor fuel. For example, all or the vaporous constituents boiling up to about the endpoint of gasoline may be passed directly from the cracking plant to the primary treating step. As an alternative, the distillate may be subjected to a hydrogen sulfide removal step, passing through line I to step 4. The hydrogen sulhde may be removed in any suitable manner, of which many are known. These include treatment with sodium hydroxide, tri-potassium phosphate, sodium carbonate, lime and others. When such procedure is used, all or part of the normally gaseous hydrocarbons may be removed through line 5. The cracked products are then heated and passed through line 6 to treating step 3. The gases and hydrogen sulfide may be removed by stabilizing the overhead from the cracking plant iractionator without resorting to chemical treatment in step 4.

In treating step 3 the gasoline is contacted with an earth or clay type treating agent which may be of a relatively adsorbent type such as iullers earth at a temperature at which gum-forming and highly colored constituents are removed, this apparently being accomplished by the polymerization of the highly unsaturated components to higher boiling liquids. It is desirable at this point to carry out a relatively mild treatment, usually within the range of approximately 250to 500 F. at substantially atmospheric or slightly superatmospheric pressures up to about 100: lbs; per square inch. It is within the scope of the invention that pressures sufficiently high to maintain a major portionof the gasoline in liquid phase may also be employed in this step.

It should be stressed that the object of this treatment is to remove highly unsaturated materials which tend to oxidize and/or polymerize readi y, these being referred to hereafter as gumforming constituents or gum formers, without substantially affecting the sulfur content .of the.

gasoline. The exact conditions used will vary with the type of treatingag'ent employedand with the distillate undergoing treatment. Relatively large quantities of gasoline may be passed through the treating agent before it is spent, the exact quantity depending upon the gasoline undergoing treatment and usually being from about 1500 to 10,000 bbls. per ton or higher. The copper dish gum content of the degenerated gaso-' line from this step may serve as a guide as to the adequacy ottreating conditionsand to determine when the treating ag nt is spent. Other Well known methods of indicating the presence of undesirable amounts of gum iorrning bodies also may be used.

During the treatment in this step higher boiling polymers are formed and these may be. removed through line 1. The treated gasoline is passed through line 8 to gas separation step 9;

This step may consist of a stabilization step wherein the normally gaseous hydrocarbons and even some of the low boiling,normally liquid'hydrocarbons are removed through line W; These gases may be subjected to catalytic polymerization to produce high antiknock motor blending fuel, after being treated to remove hydrogen sulfide therefrom. This may be subsequently blended with the finished gasolineof the present process, together with residual butanes in order to make the desired vapor pressure; Inaddition to the stabilization step thenorma-lly liquid hydrocarbons may be treated 'to remove hydrogen sulfide, for example by washing withdilute alkali or alkali metal compounds. The separation-step is not to be construed as limited-to these particular steps but rather to be viewed from itsobject, which is to separate. the normally. gaseous constituents and to remove hydrogen sulfide from the liquid hydrocarbons priorto passingsaid liquid hydrocarbons to the subsequent .desulfurizae tion step. Aftertreatment in step .9 the. liquid hydrocarbons are vaporized and superheated to a temperature above. that .usedinstep. 3..and which is usually, withinthe range. of .approx% matel 550 t b ut 9 0. d pre e ablrwith in the r n o .a r imate vfil 0.7 0? and re. t en pa ed' h qu hl ne to ea n s p I2 her n th re ntac ed Withanea th t pe reagent which may be the sameor different from that employed in treating step 3. Materials suit able for this purpose include various naturally occurring earths such as fullers earth, bentonitic clays, bauxite and the like, although these in no way are equivalent since earths of relatively low adsorbent properties are to be preferred, such as bentonitic clays, etc. One clay which is particularly suitable for use in this step is found in the neighborhood of Silverton, Texas, and is of a bentonitic type. When Water is added to it,

the particles tend to swell forming the gel-like structure characteristic of this type of earth. In large quantities of water, creamy emulsions are formed. It does not, however, tend to disintegrate upon being heated to high temperatures as is characteristic of bentonite itself. It has a relatively. high specific gravity in relation to the, usual types of fullers earth, such as those found in Georgia, Florida, Illinois, etc., weighing about twice as much per unit volume, and is much less adsorbent than these earths as is shown by the fact that it has practically no value for the filtration of lubricating oils under the usual, low temperatureconditions. The clay contains from'ap'-' proximately 42 to 50 per cent silica, approximately to 13 per cent alumina, 4 to5 per cent iron oxide, and roughly, 10 to per cent ofIi' Di ture as produced. Alkali and alkaline" earth metal compounds are present and include those of calcium, magnesium, potassium and sodium.

The treating agent may be'used in granular form or may be compressed'into various shapes suchas pellets,. spheres; etc. The earthswhi'ch may be used inthisstep may be further activated by treatment with stearn'oracids. Theitreating step |2Lis operated at a" temperature within the range aboveindicatedjandis conducted at'pr'essure conditions such that the hydrocarbons are in substantially va'ip'or form. Normally, press res are below approximately s. oersquare inch, although this may, vary somewhat- The treating conditions are. regulated to: avoid as much as possible additional polymerization of unsaturated hydrocarbons and also, to avoidflsubstanuai decomp'cisition (if urehy rocaibc'iis into lower boiling 6i. gaseous. hyd ocarbons. Thfbliditions of this step are so regulated asto obtain a substantial deereasam the. sulfur co'ziter'it of the fuel undergoing treatment .without materially affectingfth boiling range 21rd Without; excessive squi 'voluine 10st. complete uesuuuri at on' is net a ways obtained but ithasbeeh round that the sm ur compounds removed are those bf the most demmemartypemseraias their efreeton oetanenumeer and tetrathyl lead susceptibility 7 is, concerned. I

The treated Oil pas sd throli g h line [3 to fracticnation step I; ffo'rdwhich any high-boiling material is removed through-line l5; Inview of the fact that the. pibdiili frdlfl treating. Step 3 ma not be. fractioha't'e dto the exact endpoint desired but is'usually' subjected to a rough separation to remove high boiling polymers, a certain amount 6f material boiling above the. desired nepemt of gaseurie is eparated in the r setionation stepl4. The r'r'i'ot'or fuel is then passed tmousmi i ro anenamt e r atinej te 121m orderl qie e ad u f r r mova H dr gen:s lfidgrenipvaijstep sweetening .trea't Il may sometimes include a are iiiment since the gasoline may contain minor amounts of mercaptan sulfur ordinarily amounting to substantially less than 0.01 per cent.

The following specific example is given to illustrate the operability and advantages of the process, and should not be construed as limiting it to the exact conditions given therein.

A West Texas topped crude oil was thermally cracked to produce motor fuel. The vaporous reaction products having an endpoint of approximately 450 F. were passed directly from the cracking plant to treating step 3 wherein they were contacted with the Silverton clay described above, at a temperature of approximately 400 F. and a pressure of approximately 90 lbs. per square inch, in a conventional vapor phase clay treating operation. A polymer knockout drum was used whereby a major portion of the polymers produced in the treating step were removed from the system. The treated products were then passed to a stabilization step and the normally gaseous fraction was removed to a separate catalytic polymerization unit wherein the gaseous olefins were converted to high antiknock gasoline. The normally liquid products from treating step 3 were then washed with 4 per cent sodium hydroxide solution to remove the last remaining traces of hydrogen sulfide, and the gasoline was heated to a temperature of 650 F. and passed to the second treating step l2 at a pressure of approximately 35 lbs. per square inch. The quantity of clay in the first and second treating steps was approximately the same, and the charge rate was approximately 3.5 bbls. of gasoline per ton of clay per hour. The products were then fractionated to remove a minor quantity of polymer boiling above 400 F. and the gasoline was washed with sodium hydroxide solution to remove hydrogen sulfide. The finished gasoline had an endpoint of 400 F.; a copper dish gum content of 2 mg. per 100 00.; A. S. T. M. gum content of mg. per 100 00.; color of 30+ Saybolt; an oxygen bomb induction period in excess of 4 hours; and the potential gum content by the glass dish method after four hours in the oxygen bomb was 2 mg. per 100 cc. of gasoline, indicating a high degree of stability. The gasoline directly from the first treating step contained 0.35 per cent sulfur (approximately the same as that from the cracking plant), of Which 0.12 per cent Was mercaptan sulfur. The sulfur content of the finished gasoline was 0.16 and the mercaptan content was less than 0.005.

The octane number of the gasoline charged was 66.5 and after treatment 69.0. The octane number of the original gasoline with 3 cc. of tetraethyl lead added was 75.5, while that of the treated gasoline was 79.

These results were obtained after a yield of approximately 3000 barrels of gasoline per ton of clay had been processed in the first step and 1200 barrels per ton of clay had been passed through the second step. When treating the gasoline directly from the cracking plant under the conditions used in the second step of the present invention, the yield of gasoline of comparable properties obtainable was approximately 200 barrels per ton of clay. Thus it may be seen that the total yield of gasoline of properties such as those obtainable by the present process may be increased by at least ten times over that which may be obtained when using a single step procedure.

I have found that the primary treating step improves the efiiciency of the secondary treating step. This is undoubtedly due to a combination of factors, which may include the conditioning of the sulphur compounds by the primary step to forms more readily removed or converted in the secondary step.

I claim as my invention:

1. The process of refining gasoline that comprises treating the gasoline in a first stage by contacting it with adsorbent clay at a relatively low temperature to effect polymerization of unstable gum-forming constituents, separating resultant polymers from the treated gasoline, heating the treated gasoline in a second stage to a temperature of the order of 650 F.750 F. and contacting it with adsorbent clay to effect desulfurization.

2. The process of refining gasoline that comprises contacting gasoline vapors with adsorbent clay at a relatively low temperature to eifect polymerization of unstable gum-forming constituents, separating resultant polymer products from the treated vapors, heating the treated vapors and contacting them with adsorbent clay at a temperature of the order of 550 F.900 F. under conditions to effect desulfurization while substantially avoiding conversion of gasoline constituents into hydrocarbons boiling outside the boiling range of the gasoline treated.

3. The process of refining gasoline that comprises treating the gasoline in a first stage by contacting it with fullers earth at an active polymerizing temperature of the order of 250 F.- 500" F. to eifect polymerization of unstable gumforming constituents, separating resultant polymers from the treated gasoline, heating the treated gasoline to raise the temperature thereof and contacting it with fullers earth while maintained at a temperature of the order of 550 F.900 F. under conditions to effect desulfurization while substantially avoiding conversion of gasoline constituents into hydrocarbons boiling outside the boiling range of the gasoline treated.

FRANCIS HAROLD BOTTOMLEIY. 

